The present disclosure pertains to the field of information processing, and more particularly, to the field of managing interrupts in an information processing system.
Generally, the concept of virtualization in information processing systems allows multiple instances of one or more operating systems (each, an “OS”) to run on a single information processing system, even though each OS is designed to have complete, direct control over the system and its resources. Virtualization is typically implemented by using software (e.g., a virtual machine monitor (“VMM”)) to present to each OS a virtual machine (“VM”) having virtual resources, including one or more virtual processors, that the OS may completely and directly control, while the VMM maintains a system environment for implementing virtualization policies such as sharing and/or allocating the physical resources among the VMs (the “virtualization environment”). Each OS, and any other software, that runs on a VM is referred to as a “guest” or as “guest software,” while a “host” or “host software” is software, such as a VMM, that runs outside of the virtualization environment.
A physical processor in an information processing system may support virtualization, for example, by supporting an instruction to enter a virtualization environment to run a guest on a virtual processor (i.e., a physical processor under constraints imposed by a VMM) in a VM. In the virtualization environment, certain events, operations, and situations, such as external interrupts or attempts to access privileged registers or resources, are typically intercepted, i.e., cause the processor to exit the virtualization environment so that a VMM may operate, for example, to implement virtualization policies (a “VM exit”).
Therefore, external interrupts may be intercepted by the VMM and routed to the appropriate virtual processor. Alternatively, a virtualization environment may provide for external interrupts to be routed to a virtual processor without a VM exit, for example, if the interrupt request is generated by an input/output (“I/O”) device assigned to the currently active VM, or if the interrupt request is an inter-processor interrupt between two virtual processors in the same VM. Whether the interrupt request causes a VM exit or not, routing the interrupt to the appropriate virtual processor may include mapping interrupts requests from a guest's view of the system to a host's view of the system. In existing information processing systems, the VMM may be responsible for remapping interrupt requests whenever a virtual processor is migrated from one physical processor to another physical processor.